Efficient low-power TOBSY sequences for fast MAS.

Area of Science:

• Solid-state Nuclear Magnetic Resonance (NMR) Spectroscopy
• Physical Chemistry
• Materials Science

Background:

• Through-bond J-coupling experiments in solid-state NMR are hindered by small J-couplings relative to strong dipolar couplings.
• Low polarization transfer efficiency in J-coupling experiments is often due to second-order cross terms causing rapid magnetization decay.

Purpose of the Study:

• To develop efficient polarization transfer methods for solid-state NMR using through-bond J-couplings.
• To suppress detrimental second-order cross terms in J-coupling based NMR sequences.
• To evaluate the performance of novel symmetry-based sequences under various experimental conditions.

Main Methods:

• Utilized symmetry-based C9 sequences designed to suppress second-order cross terms.
• Performed experiments on fully protonated two-spin model systems and ubiquitin samples.
• Investigated transfer efficiencies at high magic angle spinning (MAS) frequencies (55.5–111.1 kHz) and varying proton Larmor frequencies (400–850 MHz).

Main Results:

• Achieved efficient polarization transfers up to 80% without decoupling.
• Demonstrated high transfer efficiency using C9 sequences (C9₃₉¹ and C9₄₈¹) on model systems and ubiquitin.
• Analyzed the impact of radiofrequency (rf) field inhomogeneity and crystallite selection on transfer efficiency.

Conclusions:

• Symmetry-based C9 sequences offer efficient and practical solutions for through-bond J-coupling experiments in solid-state NMR.
• These methods overcome limitations of traditional sequences, enabling robust polarization transfer.
• The developed TOBSY sequences are applicable across a wide range of experimental conditions relevant to structural and dynamic studies.